We have shown that pneumonectomy in the adult animal is a potent stimulus to compensatory lung growth. This process is rapid in onset, and formation of new connective tissue components appears to be an important factor in the growth process. The postpneumonectomy state provides a unique opportunity to study collagen and elastin synthesis in the adult lung in a well defined growth model not complicated by the special circumstances of previously employed models of in vivo elastin synthesis such as fetal tissue growth or rare spontaneous or induced disease states. Using the postpneumonectomy lung growth model, we will study the sequence of elastin synthesis in the lung, investigating the dynamics of lysyl oxidase (the initial and possibly only elastin crosslinking enzyme), and elastin synthesis and maturation. We will define the factors controlling this process and will correlate biochemical events and elastin structure with physiologic studies of lung elasticity. The dynamics of elastin synthesis in this system will be compared with and contrasted to connective tissue formation during normal postnatal lung growth. Thus, these studies will provide information about the mechanisms, sequence and control of lung elastin synthesis, its physiological significance, and will, in addition, shed light on mechanisms and control of compensatory and normal lung growth. BIBLIOGRAPHIC REFERENCES: Burki, R.E., Brody, J.S. and Kaplan, N.B.: Cellular aspects of compensatory lung growth following pneumonectomy. Clin. Res., in press, 1976. (Presented at American Society for Clinical Investigation Meetings, Atlantic City, 1976.) Brody, J.S., Manalo, A., Kagan, H. and Gonnerman, W.A.: Lysyl oxidase: Regional concentrations during normal and hypoxia induced lung growth. American Review of Respiratory Disease, in press, 1976. Presented at American Thoracic Society Meetings, New Orleans, 1976.